1. Field of The Invention
The present invention relates to a wrapper, and more particularly to an automatic wrapper that can wrap a package easily and tightly.
2. Description of Related Art
A conventional wrapper in accordance with the prior art shown in FIG. 5 and FIG. 6 comprises a thermal welding and cutting device (90), a tape operating device (60) attached to the thermal welding and cutting device (90) to control the feeding and reversing of the tape (80) and an electromagnet (70) mounted on the tape operating device (60) to control the tape operating device (60).
The tape operating device (60) includes a base member (600) that has a feed roller (61) and a reverse roller (62) each pivotally mounted thereon. A support (63) has a tape roller (632) pivotally mounted on a first end and a second end fastened to the thermal welding and cutting device (90). A pair of brackets (631) extend from the support (63) to pivotally attach to the tape operating device (60) between the feed roller (61) and the reverse roller (62) to allow the base member (600) of the tape operating device (60) to pivot on the support (63).
The electromagnet (70) includes a Z-shaped plate (72) which has a first end penetrated by an actuating rod (71) and a roller (751) pivotally mounted on the second end. A spring (711) is mounted around the end of the actuating rod (71) that extends through the Z-shaped plate (72) and is held in place by a nut. The electromagnet (70) is enclosed by a case with an L-shaped connecting plate (731) is welded to the case. An auxiliary rod (73) is attached to the connecting plate (731) with a first spring (733) mounted around the auxiliary rod (73) and abutting the connecting plate (731). The auxiliary rod (73) extends through the Z-shaped plate (72) and compresses the first spring (733) between the Z-shaped plate (72) and the connecting plate (731). A second spring (734) is mounted around the end of the auxiliary rod (73) that extends through the Z-shaped plate (72) and is held in place by a nut. An active rod (74) has a third spring (742) mounted around a first end attached to the Z-shaped plate (72)and an adjusting knob (741) that is held in place by a nut. The active rod (74) has a second end attached to the base member (600) of the tape operating device (60). A roller (751) is attached to the second end of the Z-shaped plate (72) and rides on a cam (75) driven by a motor (not shown).
To operate the wrapper, referring to FIG. 7 the active rod (74) of the electromagnet (70) pulls the base member (600) to make a gap between the reverse roller (62) and the support (63) and to allow the tape (80) to pass therefrom. Then the tape (80) is pulled to a certain length due to the rolling of the feed roller (61). The operator pulls the free end of the tape (80) around the package (81) and inserts the tape (80) into the thermal welding and cutting device (90) it touches the sensor (91).
Referring to FIGS. 6 and 8, the cam (75) pushes the Z-shaped plate (72), and the active rod (74) raises the base member (600) up. Then the reverse roller (62) squeezes and reverses the tape (80) to ensure the package (81) is wrapped tightly. Then the thermal welding and cutting device (90) welds and cuts the tape (80).
No doubt the conventional wrapper can wrap the package, but the tape operating device (60) and the electromagnet (70) have several disadvantages.
1. The structure of the tape operating device (60) and the electromagnet (70) are very complicated. The tape operating device (60) must have a base member (600) with a feed roller (61) and a reverse roller (62) mounted thereon. An auxiliary rod (73) and a Z-shaped plate (72) are connected to the electromagnet (70). Furthermore ringed a first spring (733) and a second spring (734) must be around the auxiliary rod (73), a third spring (742) needs to be mounted around the active rod (74) that connects to the base member (600), and an adjustment knob (741) must be mounted on the active rod (74). The structure has so many parts and is so complicated that the cost of the wrapper is high.
2. The positions of feeding and reversing are not very stable. Whether the tape operating device (60) is feeding tape (80) or reversing tape (80) depends on the lever motion of the base member (600) to make the feed roller (61) and the reverse roller (62) squeeze or release the tape (80). Consequently, the Z-shaped plate (72) is always moving up and down. To keep the tape operating device (60) in position to reverse the tape (80) depends to the elasticity and strength of the first spring (733) and third spring (742). The mass of the base member (600) is large, so the load on the reversing tape (80) is very heavy. Wrapping the package (81) tightly or a very smooth tape (80) surface may cause the base member (600) use the pair of pivotal seat (631) as a fulcrum and swing back. Consequently, the wrapping is often not good because the reverse roller (62) releases the tape (80) when the load is heavy.
The present invention has arisen to mitigate and/or obviate the disadvantage of the conventional tape operating device of a wrapper.